International Business Machines Corporation

Donavon W Johnson

Todd A Smith

Stephen P Morgan

Amal A Shaheen-Gouda

Larry K Loucks

Larry W Henson

Charles H Sauer

Grover Herbert Neuman

Richard Alan Vrba

Louis Michael Hornung

William Clyde Cockerill

The system and method of this invention authorizes a process running at a client data processing system to have access to a service at a server data processing system. The data processing systems are connected by a communication link in a distributed processing environment. A set of credentials for the process are created at the server in response to a message from the client requesting a service. The server returns a credentials id identifying the created set of credentials to the client process. The client uses this returned id in subsequent requests and is authorized access as controlled by the set of credentials identified by the returned id in the subsequent request. The server can deny access to the service by the process if the id returned in a subsequent request is determined by the server not to identify the set of credentials. The server denies the access if the server requires an authentication of the process.

Remote authentication and authorization in a distributed data processing

A distributed data processing system and method in which locks on a file are supported by a data structure that resides on either a client machine or on the file's server. When only a single client's processes are locking a file, the data structure can reside on that client. Whenever a plurality of client machines attempt to place locks on a file, the data structure is moved to the server; this forces the clients locking the file to communicate with the server when performing lock operations. When a client requests a lock from the server that cannot be granted because of an existing blocking lock, the client is informed that it should put the requesting process asleep awaiting a retry notification. When there is a change in the locks on the file that might allow such a client's now sleeping process to acquire the lock, the server sends a retry notice to the client. This awakens the sleeping process at the client, and the process then reattempts the lock operation by sending a message to the server.

File lock management in a distributed data processing system

A distributed file management system (DFS) with a plurality of nodes and a plurality of files is disclosed. The DFS uses the UNIX operating system tree structure employing inodes (data structures containing the administrative information of each file) to manage the local files and surrogate inodes (s.sub.-- inode) to manage access to files existing on another node. In addition, the DFS uses a file access structure lock (fas.sub.-- lock) to manage multiple requests to a single file. The primary reason for the addition of the fas.sub.-- lock for each file is to avoid the problem of deadlocks. The inodes and s.sub.-- inodes use the fas.sub.-- lock to synchronize their accesses to a file and avoid a deadlock situation where both s.sub.-- inode and inode await the use of a file that is locked by the other.

Distributed file access structure lock

A system and method in which client access to data at a server is synchronized to keep the data consistent by ensuring that each portion of the data accessible for modification at a node is not accessible for reading or modification by any other node, while allowing portions of the data accessible only for reading to be accessible by any number of nodes. If a conflicting request arises from a different client the server must revoke data that has been previously distributed to a client. For a revoke.sub.-- bytes request, all outstanding get.sub.-- bytes are marked so that the bytes that are being requested to be revoked will be discarded when they do arrive at the client. To insure that read and write system calls on a file are performed in a serializable fashion throughout a distributed environment, each machine at which a read is being performed must acquire a read token and each machine at which a write is being performed must acquire a read/write token from the server for the file. When any machine has a read/write token, no machine is allowed to have a read token, although any number of machines may have a read token at the same time. The server coordinates the distribution of these tokens by revoking all read tokens whenever a write token is requested and revoking the write token whenever any read token is requested.

System and method for controlling client machine access to a portion of

An improved directory caching technique is provided for a plurality of data processing systems which are connected together in a network. In the system, when a local, or client, data processing system interrogates a remote, or server, data processing system for a unit of directory information, the server system is enabled to automatically send additional units of pertinent director information back to the client system in response to a subsequent change in the directory structure of the server system. If the server system is unable to continue updating the client system, for any of a plurality of possible reasons, the server system informs the client system of this fact, which enables the client system to purge itself of the formerly stored directory cache entry relative to this path, since the client system can no longer consider this cached path information to be currently correct.

Directory cache management in a distributed data processing system

A system for an efficient message handling technique implemented in AIX, an operating system derived from UNIX System V, is described for use in a distributed services network include a plurality of multi-processing, multi-tasking nodes among which interprocess communication occurs via queues, the actual node locations of which are transparent at the application interface.

Interprocess communication queue location transparency

The system and method of this invention maintains the latest file attributes such as file size, modify time, and access time, at the server data processing system in a distributed data processing system. The server data processing system combines information requested from the client data processing system that has permission to write to the file with information periodically received from other client data processing systems that may be extending the same file by mapping the file into their own virtual address space. In this way, the server can maintain the latest file size attribute even when some clients are extending the file through system calls and other clients are extending the file through mapped access. To maintain a latest modify time and access time, the server keeps a modify count and access count. The client data processing systems periodically send to the server data processing the modify count and access count that have been incremented whenever the client data processing system modifies and accesses the file. The server data processing system compares the counts at the server with the counts received from the clients to determine a latest corresponding modify time and access time.

Maintenance of file attributes in a distributed data processing system

These master system files define the system characteristics that a user at any node in the system can expect to have. The master system files are mounted remotely from each of the nodes of the system and a local copy of the master system files is kept locally reflecting the current contents of the master system file. If a master system file is not available, the local copy is used in read only mode until the node containing the master is available. In addition, each user has its own file tree organization that dictates the necessary remote mounts of directories to enable a user logged on to any node to have the same view of the system that would be obtained from any other node in the system by that user.

Single system image uniquely defining an environment for each user in a

A distrbuted services program installed on each of a plurality of data processing systems in a network allows the processors to access data files distrbuted across the various nodes of the network. To reduce the network traffic overhead when files at other nodes are accessed, and to preserve the file system semantics, i.e. the file integrity, the accessing of the various files are managed by file synchronization modes. A file is given a first synchronization mode if a file is open at only one node for either read or write access. A file is given a second synchronization mode if a file is opened for read only access at any node. A file is given a third synchronization mode if the file is open for read access in more than one node, and at least one node has the file open for write access. If a file is in either the first or second synchronization mode, the client node, which is the node accessing the file, uses a client cache within its operating system store the file. All read and writes are then sent to this cache. If a file is in the third mode, all read and write requests must go to the server node where the file resides. The node accessing the file does not use the cache in its operating system to access the file data during this third mode.

System and method for accessing remote files in a distributed networking

Logic circuitry is provided for controlling the transfer of data between 1) a low cost pipelined processor and its associated memory, 2) between the processor and input/output devices, and 3) between the input/output devices and memory. A plurality of unidirectional busses are provided to interface the processor and memory and a bidirectional buss is provided to interface with the input/output devices. The logic circuitry provides a control function to steer data over the proper buss structures interconnecting the processor, the memory and the input/output devices and provides those interconnections in a manner which allows the processor to overlap input and output functions.

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Georgetown, TX, United States of America

Donavon W Johnson